If your worried about the stink just switch to ethanol
550whp — do I really need a full exhaust? Or are dps and 335is muffler good enough?
- Thread starter drunkentrader
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@drunkentrader if you are still debating lol I have the vrsf exhaust sitting in my garage unused although I can't imagine what the shipping cost would be...
@SLOWESTN54 that could be why I don't notice any offensive exhaust smell..I have been running straight E85 for as long as I can remember..I might aught to run a few tanks of 93 give the car a little flushing....naaaaa faaaaak that feels too slow that way..
@SLOWESTN54 that could be why I don't notice any offensive exhaust smell..I have been running straight E85 for as long as I can remember..I might aught to run a few tanks of 93 give the car a little flushing....naaaaa faaaaak that feels too slow that way..
I didn't realize how bad 91 smelled until i was forced to switch to it, we ran out of E85 because of flooding.
@drunkentrader I'd make the switch to ethanol if possible, It smells great.
I’m running motiv flex fuel now, usually around e50-55. I might give it a shot swapping in 1792 vibrants for the cats.
Typically the correct sized exhaust is designed by measuring the exhaust gas back pressure on the existing one, if it exists.
The literature is giving some basic numbers by which one can orientate.
So while ppl state that our exhaust is "good" for xxx whp they simply take dyno numbers of what some cars achieved with a certain setup. But in reality the turbos are working against back pressure which is simply too high. This results in increased wear and more importantly loosing some of them horses.
So. No. The Stock exhaust is not "good" for 550whp although it "works".
I am not 100% sure but your maximum boost to back pressure ratio should be 1:2.
Just check this video for a few seconds:
The literature is giving some basic numbers by which one can orientate.
So while ppl state that our exhaust is "good" for xxx whp they simply take dyno numbers of what some cars achieved with a certain setup. But in reality the turbos are working against back pressure which is simply too high. This results in increased wear and more importantly loosing some of them horses.
So. No. The Stock exhaust is not "good" for 550whp although it "works".
I am not 100% sure but your maximum boost to back pressure ratio should be 1:2.
Just check this video for a few seconds:
By that chart granted I haven’t watched the video the stock exhaust is 2.25” approx x 2= 4.5” shows to be around 1,000 crank hp..
People often say dumb shit about exhausts. Example:
https://www.speedwaymotors.com/the-toolbox/choosing-the-right-exhaust/28758
"rule of thumb, that for every 100 horsepower, 1 inch of total pipe diameter is needed across the system. For example, a 500 horsepower engine would require a 5-inch exhaust pipe" <--They are talking crank too. So a 800whp N54 should have a 10 inch wide downpipe and exhaust? Pahlease. Even saying an 8 inch exhaust is bonkers.
So a 3.5'' exhaust the max HP is 468?
<-- The cup demonstration is 100% crap. Summit should be embarrassed for allowing this ever on the internet. 425-500HP needs a 4.5'' single exhaust? 400hp needs Dual 2.5'' ??? I guarantee they are talking crank and not wheel.
With a turbo you want to keep backpressure 1-1 but that rarely happens. Most say 1.5-2 to 1 is acceptable and over that you need a bigger housing or better exhaust setup. 3:1 stay away! The reality is we can't fit much more than a 3-3.5'' downpipe on a ST or 3'' DPs on twins and for the rest of the exhaust you are basically limited to a single 3.5'' or dual 2.5''. With ST you can increase the housing but there are inherent limits in everything.
Thus I have come to the conclusion that the only real solution is a 5inch stove pipe out of the hood:
https://www.speedwaymotors.com/the-toolbox/choosing-the-right-exhaust/28758
"rule of thumb, that for every 100 horsepower, 1 inch of total pipe diameter is needed across the system. For example, a 500 horsepower engine would require a 5-inch exhaust pipe" <--They are talking crank too. So a 800whp N54 should have a 10 inch wide downpipe and exhaust? Pahlease. Even saying an 8 inch exhaust is bonkers.
How To Calculate Muffler Size and Exhaust Pipe Diameter | Exhaust Videos
If you're a math wiz and/or an engineer, you're probably going to like this article and the resources we've linked to. However, if you find yourself getting stuck (or bored) with the info below, here are the key take-aways: 1. The factory exhaust pipe diameter is usually a good choice for most...
www.exhaustvideos.com
3 1/2 | 8.95 | 1029 | 468 | 935 |
With a turbo you want to keep backpressure 1-1 but that rarely happens. Most say 1.5-2 to 1 is acceptable and over that you need a bigger housing or better exhaust setup. 3:1 stay away! The reality is we can't fit much more than a 3-3.5'' downpipe on a ST or 3'' DPs on twins and for the rest of the exhaust you are basically limited to a single 3.5'' or dual 2.5''. With ST you can increase the housing but there are inherent limits in everything.
Thus I have come to the conclusion that the only real solution is a 5inch stove pipe out of the hood:
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Crank on the bottom. So 400 crank is good with dual 2.25 according to this chart which is what the N54 comes with stock. Now to convert crank to wheel we use 15% 400 * .85 = 340 whp which is about what an N54 makes on MHD stage 1/2 on 93 octane. Does anyone believe the stock exhaust is a restriction above 340whp?
Well crap, now im going to have to respray my hood. My dual 2.5s just won't cut it ☹
Nice link lol now I'm gonna have to put this onto my Mathcad and see what results I get. As typical I'm gonna have to over anal it ... well right after I finish dropping my transmission...I've turned a clutch an turbo install into a week long project already
I wrote that literature gives you somewhat an idea of where to go. Actually i focused on back pressure and that it should stay within a reasonable ratio. Just like the 2k hp gtr went for a 1:1 ratio at full boost.
But one thing is for sure. The stock exhaust is not ideal for 550whp.
I have yet to see anything that proves the stock exhaust is a restriction at 550whp. The graph above is as laughable as the links I shared.
The 2000whp GTR in that video has a 5'' downpipe. In your opinion would 1000whp would be fine with a downpipe half the size?
The way the GTR is dealing with reducing backpressure is by having a MASSIVE turbine housing and wheel wouldn't you agree?
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I have the feeling you really want to understand me wrong.
This was an example. Yes Turbo geometry has also a role in that.
What about the Z4 35i exhaust? There is a ridiculous thinning on the right side of the exhaust after the catalysts. I ordered myself a FOX x-pipe to replace that thin part. I wonder if that has an effect on power. Random image from the web.
I don't want to understand you wrong, I generally enjoy your posts but I prefer facts over conjecture. Below is what I understand about BP/exhausts etc. Anyone please feel free to correct me:
I still don't see any proof @ 550whp on an n54 that the stock exhaust is a restriction worth talking about(assuming you have 3'' catless downpipes which is the norm).
The small stock turbos which came with 10Ts and now people throw in 19 and 20T wheels in, literally twice as large compressor wheels. The high backpressure, which you read before the turbo in the exhaust manifold between the turbine wheel and the exhaust valves, comes from the VERY small turbine housing's AR which can't be fixed without a new casting which is what RB VTT and MMP did. If requiring or installing a larger exhaust would have fixed the backpressure issue that is what the twin manufacturer's' would require(Ignore DAW and their stolen warranty language). Of those 3 only 1 has had good luck with the turbos holding together which is RB with their Game Finishers. VTT has gone through like 4 or 5 different castings and companies because of failures and MMP is well...MMP(are they still in business?) failures and laggy given the larger primaries than needed.
Basically you need to increase the turbine's AR to reduce the backpressure assuming your exhaust flows fine after the turbine wheel/downpipe: https://www.garrettmotion.com/news/...n-a-r-makes-for-optimizing-your-turbo-system/
This is what the GTR did in the video you posted they have a massive turbine side and large AR. 1:1 is ideal but it can be laggy, great for top end all out power like that GTR is probably used for. I bet it sucks to drive around town compared to TT n54 as an example that large turbo and AR spools VERY late. 2:1 would spool better. Smaller AR better spool, worse top end. Larger AR better top end, laggier spooling. It is all a trade off at some point and it's just physics: we are spinning up wheels with exhaust gases in manifolds. Larger heavier wheels = laggier assuming the AR stays the same. You can push and pull the hp/tq curves on a dyno chart left and right. Example:
If the stock exhaust was the restriction causing the backpressure aftermarket exhausts would be very common on this platform and would be what you upgrade 1st. After 16 years that the N54 has existed I don't think 2022 is going to be the year of everyone ditching the stock exhaust because it is a restriction @ 550whp. Again @Payam@BMS dropped his factory exhaust leaving just the 3.5'' downpipe at 700whp and said he did not make any more HP on the dyno.
If anyone has factual data I would love to see it and be proved wrong. We are all here to learn about our cars and their engines etc.
Yes a crush like that, a restriction vs an uncrushed pipe. Everyone should remove small crush bends at an exhaust shop if they are bad or as in your case you bought a premade pipe that fixes it.
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I was going to respond very similarly, but didnt want to get into a long ass debate for something that I feel has been established on this platform.
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